Carburetor



April 18, 1939. FIRTH 2,155,162

CARBURETOR Original Filed May 9, 1934 %Wer//07 24 0! 57% 3? and Patented Apr. 18, 1939 UNITED STATES CARBURETOR David Firth, Flint, Mich.

, assignor, by mesne assignments, to Borg-Warner Corporation, Chicago, 111., a corporation of Illinois Original application May 9, 1934, Serial No. 724,795. Divided and this application May 29,

1935, Serial No. 23,969

2 Claims.

This application is a division of my application Serial No. 724,795, filed May 9, 1934, for a Carburetor, now Patent No. 2,068,127, and relates particularly to a thermostatic control means for a carburetor.

The primary object of this invention is to provide a novel and improved thermostatic means operating automatically to control the idling speed of an engine to prevent stalling thereof when the engine is cold.

More particularly it is an object to provide thermostatic means mounted on the riser between the carburetor and the manifold, and engaging the throttle to increase the extent of throttle opening at idling when the engine is cold so as to prevent stalling.

Other objects and advantages will become apparent from the following detailed description, taken in connection with the accompanying drawing, in which:

Fig. 1 is a View partially in elevation and partially in section of a carburetor embodying features of the invention.

Fig. 2 is a fragmentary sectional view taken approximately along line 2-2 of Fig. 1.

Fig. 3 is a detailed view showing the construction of the thermostatic idling speed control. The view is taken in a plane tangent to the riser at the point of support of the cam and looking toward the front in Fig. 1.

While the invention is susceptible of various modifications and alternative constructions, it is here shown and will be described hereinafter as embodied in a dual carburetor of the up-draft type. It is not intended, however, that the invention is thereby to be limited to use in an updraft carburetor but it is intended to cover all modifications and alternative constructions falling within the spirit and scope of the invention as defined by the appended claims.

The carburetor shown comprises a main body member 5 without top or bottom wall, and a fuel bowl 6 bolted to the main body member and having a wall portion 1 extending below and closing the bottom of the body member. Within the body member 5 are two mixing chambers 8 of identical construction, only one of which is here shown, each receiving air through an inlet opening 9 communicating with an air intake tube I0 50 bolted to the body member over the opening and controlled in the usual manner by a butterfly type choke valve. The mixing chambers 8 discharge upwardly into a riser II also bolted to the body member and communicating with an intake manifold, not shown. A passage 12 is provided to receive the discharge from each of the mixing chambers, and these passages are surrounded by a heating jacket I3 through which flow the exhaust gases of the engine supplied by the carburetor. The flow of combustible mix- 5 ture through the riser is controlled by butterfly throttle valves I4 mounted on a common shaft l5 having one end projecting outwardly of the riser. Fast on the projecting end of the shaft is an idling control arm l6, and loosely mounted upon the shaft is a manual control lever I'l engaging a pin IS on the arm I 6 to swing the throttle to open position. Means, not shown, bias the throttle valves to closed position.

In each half of the carburetor is a large direct 15 passage 20 leading from the inlet opening 9 to the mixing chamber 8 and controlled by a suction operated air valve 2|. A by-pass air passage 22 for primary air leads from the inlet opening 9 around the air valve and terminates in an upwardly directed venturi 23 discharging into the mixing chamber. The air valve 2| is of the flap type and is disposed obliquely across the passage 20 with its lower edge pivoted on a horizontal shaft 24 extending transversely of the body member 5 and with its upper and free edge disposed adjacent a side wall of the member. The air valve 2| operates in a well-known manner by suction within the carburetor, which is a function of the degree of throttle opening. Dashpot 30 means housed at 25 is provided for normally maintaining the air valve in position to close the passage 29 and for calibrating the valve to varying degrees of opening in proportion to the amount of suction within the carburetor. This means is more particularly disclosed in my copending application above referred to.

Fuel is supplied to the mixing chamber by a plurality of means supported in the wall portion I of the fuel bowl. At all speeds of the engine, fuel is discharged directly into the mixing chamber 8 through a nozzle 26 vertically disposed and terminating within the venturi 23. At intermediate speeds additional fuel is supplied by a jet 21, and at high speeds a jet 28 comes into operation. The jets 21 and 28 are disposed on the inlet side of the air valve and are controlled thereby to discharge additional fuel successively as the degree of opening of the air valve increases. In order to prevent vapor bubbles from entering the supply passages for the nozzle and jets and cause what is known as vapor lock, the nozzles and jets terminate in slender tubes 29 and a stud 30, having a duct 3| formed therein, ll

extending downwardly into a sump 32 just short of the bottom thereof.

Disposed in the duct 3| is a calibrated jet 32 discharging into an enlarged portion 33 of the duct. The jet 32 usually is smaller than the jet 2! and in the normal operation of the carburetor governs the amount of fuel supplied by the jet 21. In order to discharge additional fuel into the carburetor during the power range of operation, auxiliary throttle controlled means is provided for supplying additional fuel to the intermediate speed jet directly and not through the jet 32. In the present instance, this auxiliary means comprises a duct 34 terminating at one end in the enlarged portion 33 of the duct 3| and communicating at the other end with the fuel bowl 6. At the end communicating with the fuel bowl, the duct 34 is controlled by a valve means 35, more particularly disclosed and claimed in my copending application above referred to. Generally this means comprises a valve member 36 normally urged to closed position by a spring 31 and having an upwardly projecting stem 38.

Suitable mechanism is provided for actuating the valve 36 in accordance with the position of the throttle to provide for the supply of additional fuel to the intermediate speed jet during the power range of operation. In the present instance this mechanism comprises a cam 40 disposed above the stem 36 of the valve and fast on a shaft 4| extending transversely of the fuel bowl with one end projecting outwardly thereof. The outwardly projecting end of the shaft 4| has fixed thereon a crank arm 42 connected by link 43 to arm l6 fixed on the projecting end of the throttle shaft I5. The contour of the cam 40 is such that when the throttle is substantially closed the valve 36 also is closed, and when the throttle is opened to the power range of operation the valve is opened to permit flow of additional fuel to the intermediate speed jet 21.

Means is provided for automatically varying the degree of throttle opening when the engine is idling in order to prevent stalling of the engine. This means is controlled in accordance with the heat of the engine and in the present instance comprises a cam member 45 rotatable on a sleeve 46 held fast by a screw cap .41 on a stub shaft 48 threaded into the riser II. The periphery of the cam is formed with a dwell surface 49, a stepped portion 50 growing progressively radially away from the axis of the cam, and a dwell surface 5l. Abutting the periphery of the cam is a set screw 52 on the idling control arm l6 fixed on the projecting end of the throttle shaft.

Within an annular housing formed by a flanged member 53 rigid with the inner face of the cam member 45 is a spirally coiled bimetallic element 54 having its inner end secured in the sleeve 46. The outer end of the bimetallic element 54 is bent into a hook 54 and engages in a slot 55 in the flange of the member 53 to rotate the cam as the element 54 expands or contracts in accordance with the temperature of the riser. The cam carries a stop pin 56 positioned to abut lugs 51 and 58 on the riser limiting the degree of rotation of the cam. When the engine is cold, the cam will be rotated until the pin 56 abuts the lug 58 in which position the screw 52 of the idling control arm l6 rides on the surface 5i and retains the throttle open a substantial amount to increase the idling speed of the engine and thereby prevent stalling. As the engine warms up, the thermostatic element 54 rotates the cam in counterclockwise direction, as viewed in Fig. 1, thereby successively decreasing the extent of throttle opening until the engine is thoroughly warmed,

and idles properly on a minimum throttle opening as determined by engagement of the screw 52 with the surface 49 of the cam. With the thermostat located on the riser it is influenced both by the exhaust temperature and by the temperature of the combustible mixture, and thus exercises a very effective proper control of the idling throttle position.

I .claim as my invention:

1. In a carburetor having a riser heated by a the exhaust of the engine with which the carburetor is associated, a throttle valve controlling the flow of combustible mixture from the carburetor to the engine, an idling control arm limiting the closing movement of said throttle, a cam member rotatably mounted on the riser and providing a variable abutment for said arm determining the idling position of said throttle valve, a spirally coiled bimetallic strip engaging said cam member and operating in accordance with the temperature of the engine to rotate said cami to various positions increasing the idling speed of the engine when the same is cold, a pair of abutments on the riser, and means on the cam en-' gaging said abutments to limit rotation of the cam.

2. In a carburetor having a riser heated by the exhaust of the engine with which the carburetor is associated, a throttle valve controlling the flow of combustible mixture from the carburetor, an idling control arm rigid with the throttle valve, and thermostatic means for automatically controlling the idling position of said throttle valve comprising a stub shaft mounted directly on the riser, a sleeve fast on said shaft, a cam member 

